I'm going to order a barrel for my SPR/precision/coyote build. I was thinking about going with a BCM standard 16" mid, but after seeing pics of 18" guns I thought I would get some opinions. I'll mostly use it for coyote hunting, but will shoot out to 500-600yds on occasion, either 1:7 or 1:8 twist. I know stainless barrels are probably more accurate, but at this point a chrome lined bbl will be accurate enough for me.

What length and material do you recommend?

I hunt coyote with an SBR, so for fast action at the caller I believe in short.  For you the 16 inch will be a better choice.
 

I just finished the same build (still need optic) and I went with an 18'' Odin Works barrel that's guaranteed sub MOA.

Difference between 16 and 18'' isn't too noticeable to the shooter, but you'll get an additional 75-100 fps depending on what ammo you're using.

I was looking at the Odin and the Rainier barrels, I've been trying to find some info about the ballistic advantage barrels too, but I'm in the dark when it comes to the nitride (or what ever it's called)

Roughly how long is the life of stainless barrels?

For that range I would go 18” if not 20”.
I have both.
Unless I was going to be doing a bunch of walking I would typically use the 20”.

Right now my only rifle is my M1 Garand and I carry it around in the woods/field, so length and weight are not that big of a deal although I wouldn't mind a light faster rifle in case I walk up on a hog or coyote.

A 20'' AR would still be lighter than your Garand (depending on optics, of course)

Stainless barrels life is dependent on rate of fire among many other things. Usually 7-10k is a good guestimate.

While I don't do mag dumps, but quick follow up shots might be needed, Mega barrels are guaranteed to shoot sub moa at 100yds with match ammo and have the nitride coating/treatment...

Has nitride been proven to increase the life of stainless barrel?

18" Fluted SPR 3 gun barrel AR15 Performance
18" with a rifle length gas system to soften the recoil impulse for the fastest follow up shots.

223 Wylde chamber  4150 CMV  8 twist  5R , .850 under the guard, .750 gas block, .720 from the gas block forward.

Threaded 5/8-24, M4 feed ramps,  2lb 3.2oz
Flutes on barrel may not line up top dead center.
Melonite treated barrels have proven to last near twice as long as stainless barrels and are just as  accurate.

This barrel is primarily a 3 gun barrel but is also very accurate and could be a good varmint or target barrel

NOTICE*** THIS BARREL HAS 5/8-24 threads to keep the bore at the muzzle from swelling like most barrels threaded 1/2-28. The tighter bore at the crown gives better accuracy. Do not use Armalite 308 crush washers, YHM or DPMS 5/8 or 308 crush washers work better.

ADCO has a pretty good writeup about SS barrels in their industry forum.  Link

Their test barrel was an original 16" Wilson SS barrel that was cut to 11.5".  It saw FA fire as well as rapid fire in SA mode.  After 15K rounds it was still shooting great.

I think your 7-10K round ballpark is quite low if you aren't buying the barrel to bump fire rounds into a dirt berm all day every day.

18"

Thanks for the replys and the patients, it's been a few years since I've been in the AR world. Right now I'm stuck on a rainier, mega, odin, bcm or a woa barrel (not in any particular order)

I'm a big proponent of shorter barrel length, and think that 16" is a good length for a rifle chambered in .223. You don't gain any accuracy with longer barrels, but you do gain velocity. Velocity is very important for this round since the most significant tissue damage occurs when the bullet tumbles and fragments. Between a 16" and 20" barrel though, you'll only gain approximately 100 fps with most rounds, and that speed will drain off in about 25 yds. However, velocity also affects bullet drop. Up to about 300yds the bullet drop will not be affected mugh, but at 600 yds the bullet will drop about 20" more with a 16" barrel over a 20" barrel. At that range you're approaching 1000fps - although I've always suspected that changes in twist rate and flight angle plays a part in how the bullet acts at longer ranges, most people would say the .223 round isn't very effective at that range. So for effect, a 16" barrel will match every advantage of a longer barrel up to the rounds effective combat range. Of course if you only plan to ever shoot paper or steel, it will make the same sized hole no matter how fast it's going, and 20" less drop is pretty significant at 600yds. For a gun you want to stretch the capabilities of the round from a bench rest and do not plan on carrying much, a 20" barrel or even a 24" barrel has advantages.

After sleeping on it, I've decided to leave the long range shots (500+) for a bolt gun I'm working on. Still want to make shots out to 300 yards, does the 223 have enough at 300 yards to kill, coyote and hogs? I know shot placement plays a major role.

It should take care of coyotes at 300 yds no problem. Heavier bullets need less speed to fragment, and lighter bullets have for velocity to fragment with. They make soft tipped bullets for hunting. I'd look into all of them.

223 REM/5.56mm can make clean kills at 300 yards easily.
Obviously ammo selection is a key factor.
Check your state laws for what is legal.

Tennessee only allows ballistic tip, hollow point, and soft point for hunting

FWIW
I use a 16" AR.  I found out that when the wind in the desert kicks up it will try to blow your 223 bullets into the next time zone.
Usually at 11am or so.  I learned if it's windy, 300-350 yards is a little more realistic.
Doesn't matter if it's 53gr screamers or 75gr Hornady Match bullets.
When it got too windy I switched to a 270 and 130gr ballistic tips.  YMMV..

I re-checked the distance of my field and turns out it's only about 300-350 yards that's open field. I really like an 18" but I'm still having trouble deciding  between that and the 16"

For the most part I'll be shooting heavier factory hunting rounds until I get into reloading

Go 18''.

There's not much of a difference in weight and you get a decent amount of velocity from only 2''. Waiting to choose an optic (and see what's on sale ) but here's mine until then.

Just pulled the trigger on Rainier's 18" mountain barrel, Thanks for all the help